Oh dear!
I'd approach this one methodically, because it's likely there are two faults.
I think the first thing to do is check the pot is working correctly with a multimeter. The pot's ground wire being disconnected, and it still sort of worked, means the all the connections from the control panel to the VFD need to be checked. Photos would help!
Back to the pot. One end is connected to a DC source (5 or 12V) provided by the VFD, the other to a particular ground terminal on the VFD. This isn't necessarily the same as mains earth. The pot's wiper (middle connection) puts a voltage varying from DC max to DC zero on to the VFD's speed control terminal.
Confirm the pot alters the speed control volts at the terminal before doing anything else. Any hint of misbehaviour replace the pot – they are vulnerable to dirt and wear and tear. (Squirting them with switch cleaner can get them going again. Good with dirt, not with wear.)
Important to ensure the control wiring is working before reconfiguring the VFD. Messing with the VFD's internals in hope of fixing a wiring problem is likely to replace one problem with two!
However, after confirming all the connections are solid (vibration can loosen them), if it's still not working, next step is to restore the VFD's sanity.
Running the VFD from it's own control panel (if there is one) may show helpful error codes, and working OK from the back but not from the remote pendant suggests the pendant or it's connections are adrift,.
If looking at the settings doesn't highlight anything wrong, the usual procedure is to reset the unit back to factory settings (how to varies and should be in the manual), and then manually restore your local settings. This can range from difficult to easy depending on the VFD. New VFD's aimed at people like us often come sensibly preconfigured, and relatively few options. High end industrial VFDs, especially older ones, are installed by trained men, made familiar with the options and how to read the manual on a course. A very common arrangement is for these settings to be configured in an office by an expert and then copied directly to the machine. Fat lot of use that is to us!
Not sure about the Jaguar – my feeling is it's in the middle, fairly user friendly but with plenty of confusing choices.
Ron said 'Now when I power up the VFD I get a reading of 0.00 but there seems to be no communication between VFD and the remote control panel, fwd/rev switches, the on/off switches and the speed control pot are all doing nothing. When I checked the parameters I did get in a bit of a muddle at one point so dont know if I have switched something off or not, cant say.' One possibility is the pendant is disconnected, check the wiring. The other is the VFD has been put into local control, in which case it should be possible to work it from that end.
As the problem started with a speed control problem, which may have been related to the disconnected wire, I think the VFD is probably OK, though it may have been confused by Ron.
Basically the diagnostic approach is to check everything step by step, make sure all the connections are physically correct, then confirm electrical continuity, then look at the VFD. Two different problems being in play at the same can confuse diagnosis; don't get disheartened! The forum is invaluable, with luck an easy answer, more often helping navigate the maze.
Worst case the VFD and pendant can be replaced. Probably isn't necessary, touch wood!
Dave